Find Your Perfect Heart Rate Training Zone

Measuring your intensity will make every run count--and it isn't just for elites

When Joe Driscoll toed the line at the U.S. Men's Olympic Marathon Trials in November, he knew that maintaining an even pace would be trickier than usual on the rolling hills of New York City's Central Park. So instead of checking his splits every mile, as he normally would, he paid attention to how he felt, only looking at his watch every 5-K. "Instead of surging the hills to keep pace, I kept the same effort and let any time lost on the uphills come back on the downside," says Driscoll, 28, of Blowing Rock, North Carolina. The result was a personal record of 2:18:22.

Driscoll knew that in order to race well, he needed to run at the right intensity. If he had insisted on sticking to a 5:20-per-mile pace, he might have missed coming in under 2:19. The same principle applies during training. "Every workout has a goal," says Dennis Barker, coach of the elite running group Team USA Minnesota. "That goal might be recovery or to improve your lactate threshold, but if you don't run at the heart-rate zone that corresponds with those goals, you won't achieve the training effect."

So how exactly do you determine the right effort for every workout? Barker's athletes primarily use heart rate. Driscoll and his fellow runners at Zap Fitness in North Carolina favor perceived effort. Both methods are effective; choose one or the other, or a mix of both, and you'll soon learn how to hit your target every time.

Beat It

Measuring your heart rate–whether with a monitor or taking your pulse for 10 seconds–is an objective, numbers-don't-lie way of peeking inside your body to see how hard it's working. It was the tool Carrie Tollefson, a 2004 Olympian and member of Team USA Minnesota, needed to improve her running. "She wore a heart-rate monitor on easy days to make sure she was running in the recovery zone," says Barker. The slower pace allowed her to increase her weekly mileage from 60 to 90, which ultimately helped her shave 47 seconds off the 5000 meters to a new personal best of 15:04.

Hitting a "zone" means falling within a particular percentage of your maximum heart rate during every workout–for example, 65 to 70 percent for recovery runs and 88 to 92 percent for tempo workouts. Athletes like Tollefson who use heart rate say that precision is key: Unless you know what, say, 70 percent feels like, you could be running at 75, which may feel easy but is outside your target zone. For elites, recovery is where monitoring heart rate can make a significant difference, says Barker. Measuring heart rate may help mere mortals make the extra effort during interval work.

In order to effectively train in zones, you first need to know your maximum heart rate. Many people use the formula 220 minus your age–but that equation, it turns out, was just a rough estimate made in the early 1970s by researchers with the U.S. Public Health Service, who based it on studies that included smokers and patients on heart-disease medication–not your typical runner. Even recent attempts to produce a revised formula (208 - [0.7 x age] is one example) are still off by more than 10 beats for a third of the population. The best solution: figure your own max

Once you've calculated your zones and learned what they feel like, you can leave your monitor behind, which is what Team USA Minnesota runners do. The athletes wear monitors most often early in the season, paying attention to how they feel–and what pace they're hitting–in different heart-rate zones. As the season progresses, they know what each zone feels like and can usually hit their paces on perceived effort alone.

Feel It

Good news for the gadget-averse: Decades of studies indicate that athletes are surprisingly good at distinguishing among training zones by tuning in to their bodies. A 1986 study at the University of Liverpool, for instance, found that instructing runners to run at "somewhat hard" or "hard" efforts was at least as good as heart rate at predicting intensity. More recently, studies conducted by sports scientist Carl Foster, Ph.D., at the University of Wisconsin-La Crosse have shown that runners can consistently identify their tempo pace with a simple talk test–struggling to speak in full sentences means you've passed your threshold.

Foster has found that only about 10 percent of the athletes he has studied failed in their perceptions–mostly control-oriented people like lawyers and surgeons, who don't like to admit that anything is difficult. "They're on a treadmill, saying, 'This is easy. This is pretty easy. This is sort of moderate'–and then they're going backward off the treadmill."

Driscoll and his fellow Zap runners start a workout at a certain pace and slow down or speed up according to how they feel. "If you were up till three in the morning with a screaming kid or with a work project, it's okay to adjust your pace," says Pete Rea, Driscoll's coach.

While scientists measure perceived exertion using the Borg scale, which runs from 1 to 10 (or 6 to 20, depending on the version), top runners like Driscoll learn to match their target zones to physical cues like breathing. On threshold runs, for instance, Driscoll knows that his breathing will feel labored for the first few minutes as his body adjusts to the shock of the effort. "But then I settle in," he says. "As long as the breathing gets under control, the legs will usually adjust to the right pace." Learn to recognize clues from your own body and how it feels in each zone, he suggests. You'll be ready for any run–whether you're taking it easy, hammering out a threshold, or running the most important marathon of your life.